As is known, wireless telecommunication systems comprise a network infrastructure and mobile terminals. The network infrastructure generally comprises one or more interconnected management centres and radio base stations, which are organized for ensuring coverage of a given territory and communicate with a respective management centre. The mobile terminals link up to the network infrastructure through one or more of the radio base stations and may comprise, for example, cellphones, portable computers, or palmtops with radiofrequency connection functions, and the like.
The network infrastructure needs to undergo tests that will enable verification of proper operation thereof. Testing of the entire network infrastructure or of a part thereof may become necessary for various reasons. For example, in the design and implementation step, it could be necessary to verify the functions of the radio base station when in connection with one or more terminals of which it is possible to modify the behaviour in order to simulate situations of failure or errors in the communication protocol. Further, it could be necessary to verify the expected behaviour of the station radio base in the presence of network load determined by a number of user terminals that are simultaneously active.
Further, one of the most important functions of a radio base station increasingly lies in the management of the radio resources, i.e., in the capacity of optimizing the use of the available bandwidth, minimizing the interference and the requests for retransmission and maximizing the performance that may be obtained on a plurality of terminals. The most critical situations arise when the users are distributed within the area covered by the cell and especially in the so-called cell-boundary area, i.e., the boundary region between adjacent cells. These situations require accurate verifications in realistic conditions, which may not be created with the use of a single conventional channel simulator for the entire population of terminals.
One of the main problems that it is necessary to take into account in the design and implementation of tests on mobile radio-communication systems derives from the fact that, in order not to penalize the transmission throughput, frequently adjacent cells are authorized to use the same resource blocks (i.e., sets of sub-carriers for a given timeslot). The mobile terminals are frequently in motion and may frequently be located in cell-boundary regions, which are exposed to the risk of inter-cell interference. In practice, in the cell-boundary regions the communication of a mobile terminal with the serving cell may be disturbed by the signals coming from an adjacent cell that uses the same resource blocks.
Of course, to render the test campaigns more reliable, it is expedient to investigate also the inter-cell interference phenomena by appropriate simulations. Among other things, in the conditions of actual use, in a communication network numerous mobile terminals, with different movement profiles, may be simultaneously connected to a same cell.
The complexity of the telecommunication networks based on an OFDM modulation, which is due both to the modality of modulation and to the management of the radio resources, requires verification and validation techniques based upon simulation of a radio environment with a multiplicity of mobile terminals independent of one another.
However, currently available mobile-terminal simulators are not suited, as regards their structure, functions, and computational load required, for simulating the inter-cell interference phenomena with sufficiently numerous populations of mobile terminals.